In the photographic or cinematographic reproduction of documents or other fixedly positioned objects, the size of an image projected by an objective upon a receiving surface, e.g. a xerographic sheet or a photosensitive plate or film, can be varied by displacing that objective toward one or the other plane, with simultaneous adjustment of the focal length through a shifting of one or more components of the objective (i.e. lenses or lens groups) along the optical axis. With constant illumination of the object, the brightness of the image varies inversely with magnification so that a compensatory adjustment of the effective aperture ratio is also desirable.